Computer networks allow multiple computers, peripherals and other information storage, retrieval or processing devices to share data. Each device attached to a network is typically referred to as a node on the network, or a node that is part of the network. Local Area Networks (“LANs”) have historically consisted of nodes interconnected by physical telecommunications media (eg, coaxial cable, twisted pair wire, or fiber optics). Recently wireless LANs, the nodes of which are not connected by means of a physical medium, have started to appear in the market. These wireless LANs communicate by means of infra-red (IR), radio or other short-range signals. One of the benefits of using wireless LANs is that cabling is not required. This is a particularly useful feature for mobile nodes such as laptop and notebook computers, PDAs (personal digital assistants), and the like. If appropriately equipped with an appropriate wireless adapter, the mobile nodes can move around within a predefined coverage area and remain connected to the network.
Certain short-range wireless networks predicated on the proposed “Bluetooth” wireless communications protocol are currently being developed. This protocol contemplates the grouping of physically proximate wireless nodes into “piconets”. In Bluetooth networks, each encoded message packet sent from a transmitting device incorporates an access code specifying an address of a receiving device. The access code is also used to effect timing synchronization in the receiving device. The Bluetooth access code consists of a 4-bit preamble, a 64-bit sync word, and a 4-bit trailer. Since the preamble and trailer are relatively short, a receiving device may not be able to consistently use them to acquire proper timing information. For example, noise in the communication channel could lead to a bit shift, which would preclude decoding of the message information included within the received packet.
A conventional approach to acquiring timing information from similarly encoded packets is to effect a sliding correlation using the sync word. In this approach the sync word within each received packet is correlated with the access code of a target packet pre-loaded within a correlator of the receiving device. The sync word contemplated by the Bluetooth protocol is generated by prepending parity bits to the address of the receiving device so as to form a BCH (Bose, Chaushuri, Hocquenghem) code block not easily mistaken for another. The preamble, sync word and trailer of the Bluetooth access code collectively yield favorable autocorrelation properties, thereby making the access code useful for timing synchronization.
A Unfortunately, in certain applications it is desirable to receive subsequent packets containing any of a number of potential access codes. Use of the conventional synchronization approach described above would require multiple correlators (i.e., one per potential access code). Since in many applications a large number of access codes may be possible, this approach will often be infeasible. Accordingly, a need exists for a method of acquiring device address and timing synchronization information from encoded data packets which does not require a priori knowledge of potential access codes.